Well, I know that the classic 'treatment' for premature ejaculation is to practice lasting really long when you masturbate by using the stop-and-go technique; I don't know if it'll carry over to lasting longer for oral sex, but you might want to try to get your significant other to do a stop-and-go with that. Again, I have no idea if this'll help you or not, but it's the only thing I can think of. Of course, I suppose you could always do a google search on premature ejaculation treatments to see what that turns up.